Listing scheduled notifications in a table view controller - ios

Question

I am trying to list all the notifications a user has created and scheduled in my app, similar to that of the list of alarms in the 'Clock' app from apple. However, each time I get the array of notifications and attempt to display them, they are not being correctly displayed all the time.
Each notification is repeated each day at the same time, so I am using UNUserNotificationCenter.current().getPendingNotificationRequests to get an array of the notifications. With this array of notifications, I iterate over each notification, create a new custom 'Reminder' object and add it to my array of 'Reminders' which I use when I display the notifications in the table view controller.
I do this every time using the viewWillAppear function.
Here is the code:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
generateReminders()
tableView.reloadData()
}
func generateReminders()
{
let center = UNUserNotificationCenter.current()
center.getPendingNotificationRequests { (notifications) in
for item in notifications {
if let trigger = item.trigger as? UNCalendarNotificationTrigger,
let triggerDate = trigger.nextTriggerDate() {
var withSound = true
if(item.content.sound != UNNotificationSound.default)
{
withSound = false
}
self.reminders.append(Reminder(identifier: item.identifier, time: triggerDate, message: item.content.body, withSound: withSound, isAPendingNotification: true))
}
}
self.remindersCount = notifications.count
}
}
When the cells are about to be displayed in the table view controller, I use the 'Reminder' array to customise each cell to display the information of the notification. This is all done in the 'cellForRowAt' function, code below.
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Reminder", for: indexPath)
var text = ""
var detailText = ""
if(indexPath.row < remindersCount) {
let reminder = reminders[indexPath.row]
let formatter = DateFormatter()
formatter.dateFormat = "HH:mm"
text = formatter.string(from: reminder.Time)
detailText = reminder.Message
}
cell.textLabel?.text = text
cell.detailTextLabel?.text = detailText
return cell
}
When a user selects another tab to view, I reset the 'reminders' object to be empty so that when they return to this tab, an updated array of notifications is displayed, code below.
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
reminders = [Reminder]()
remindersCount = 0
tableView.setNeedsDisplay()
}
The issue I am facing is this is extremely inconsistent, sometimes all the notifications are displayed, sometimes only some are displayed and other times none of them are displayed. However, each time I print out the count of the number of notifications in the UNUserNotificationCenter.current().getPendingNotificationRequests method it is always the correct number. Furthermore, whenever I click on a cell that should contain information about a notification, the information is there, it is just not being displayed.
Here is a short video of these issues.
https://imgur.com/1RVerZD
I am unsure how to fix this, I have attempted to run the code on the main queue and on the global queue with the quality of service set to '.userInteractive' as shown below, but, still no dice.
let center = UNUserNotificationCenter.current()
let dq = DispatchQueue.global(qos: .userInteractive)
dq.async {
center.getPendingNotificationRequests { (notifications) in
for item in notifications {
if let trigger = item.trigger as? UNCalendarNotificationTrigger,
let triggerDate = trigger.nextTriggerDate() {
var withSound = true
if(item.content.sound != UNNotificationSound.default)
{
withSound = false
}
self.reminders.append(Reminder(identifier: item.identifier, time: triggerDate, message: item.content.body, withSound: withSound, isAPendingNotification: true))
}
}
self.remindersCount = notifications.count
}
}
A small application of this issue occurring can be downloaded from this Github repository.
https://github.com/AlexMarchant98/LitstingNotificationsIssue

Answer 1

There are some issues in your code of tableview as listed below.
You used static cells in your tableview which is not the proper way if you have dynamic rows.
Suggestion : Use Dynamic Prototype Cell for your tableview.
remindersCount not required at all as its already there in your array count.
Suggestion : Use self.reminders.count for array count.
unwindToRemindersTableViewController() method have generateReminders() call which is not required as viewWillAppear() will call when view dismiss.
Suggestion : Check ViewController life cycle you will get proper idea how to reload data.
I have updated some code in your sample project.
Please find updated code here.
Github updated demo
Hope this will helps!

Answer 2

The problem with your code is the timing when tableView.reloadData() gets executed.
UNUserNotificationCenter.current().getPendingNotificationRequests() is a asynchronous call and therefore the reminders array gets filled after tableView.reloadData() was called.
Moving tableView.reloadData() to the end of the callback-block of getPendingNotificationRequests() should fix your issue. (And don't forget to trigger the reloadData() from the main thread)
func generateReminders()
{
let center = UNUserNotificationCenter.current()
let dq = DispatchQueue.global(qos: .userInteractive)
dq.async {
center.getPendingNotificationRequests { (notifications) in
for item in notifications {
if let trigger = item.trigger as? UNCalendarNotificationTrigger,
let triggerDate = trigger.nextTriggerDate() {
var withSound = true
if(item.content.sound != UNNotificationSound.default)
{
withSound = false
}
self.reminders.append(Reminder(identifier: item.identifier, time: triggerDate, message: item.content.body, withSound: withSound, isAPendingNotification: true))
}
}
self.remindersCount = notifications.count
DispatchQueue.main.async {
self.tableView.reloadData() // <---------
}
}
}
}